Workpiece Plating Treatment Method and Workpiece Manufacturing Method

ABSTRACT

A workpiece plating treatment method includes the steps of cleaning an outer surface of an outer plating layer of a workpiece to remove a plurality of oxides and dirt on the outer surface of the outer plating layer, and reflow melting the outer plating layer of the workpiece using a reflow melting device after the cleaning.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date under 35 U.S.C. §119(a)-(d) of Chinese Patent Application No. 202210570367.1, filed onMay 24, 2022.

FIELD OF THE INVENTION

The present invention relates to a workpiece plating treatment methodand a workpiece manufacturing method.

BACKGROUND

Although the electrical conductivity of low melting point metal platingsuch as tin, indium, bismuth, and lead plating is not as good as that ofprecious metals such as gold and platinum, they also rank among the topof most metals, especially tin plating, which is widely used in thewelding and crimping of electronic connectors and their mating ends,such as PCB s, due to its low melting point, good ductility, and lowprice. With the rapid development of press fit technology, as well asthe increasing demand for connector robustness in mobile applicationssuch as automotive applications, press fit applications are increasinglyreplacing complex welding. However, in order to maintain sufficientcrimping retention force (pull-out force) to prevent the connection fromloosening due to vibration and maintain a sufficiently low contactresistance, the insertion force of crimping is too large, which can leadto two problems. The first problem is the difficulty of assembly andinsertion, and excessive damage to the tin plating layer at both ends ofthe mating. The second problem is that insertion damage can exacerbatethe growth of tin whiskers in the tin plating layer, which can lead to ashort circuit between adjacent terminals or PCB lines.

In order to solve the above problems, reflow tin melting technology wasapplied. The principle is that the tin plating layer is cooled andrecrystallized after melting, and an intermetallic compound is formedbetween the freely molten tin and the base layer or intermediate platinglayer. The hardness increases, the wear resistance decreases, thesurface roughness decreases, and the friction coefficient decreases.Under the same pressing force, the insertion force decreases (insertionforce=friction coefficient*positive pressure). At the same time, theinternal stress of the tin plating layer is released after remelting,further reducing the risk of tin whiskers. Currently, the common methodsfor reflow tin melting are to use electric furnace resistance wires tomelt tin plating, infrared thermal radiation baking to melt tin plating,or inductive heating to melt tin plating.

However, in prior art, no matter which method is used to reflow melt tinplating, the problem of uneven melting of tin plating cannot be solved.There are two main reasons for this problem:

The first reason is that the tin plating workpiece before reflow meltingcan be oxidized and contaminated through multiple processes such asassembly. Even if the fresh tin plating just obtained from theelectroplating production line is subjected to drying and otherprocesses, the tin plating surface is more or less oxidized, and themelting point of tin oxide is as high as 1630° C., while the meltingpoint of tin is only 232° C. Therefore, during the reflow melting tinplating process, the inclusion of tin oxide can cause uneven wetting andasynchronous melting, resulting in shrinkage, porous bulging, and otherproblems.

The second reason is that, during the reflow melting tin platingprocess, the molten tin interface reacts with oxygen in the air at hightemperatures to generate tin oxide, which affects the contact resistanceand friction coefficient during subsequent use. Although inert gasessuch as nitrogen or argon are commonly used in the industry forprotection, many non-hermetic processes are not suitable for theextensive use of inert gases. At the same time, due to the limitationsof product structure, different parts of the tin plating surface havedifferent heat absorption rates, which can also lead to asynchronousmelting, cooling, and recrystallization, and also lead to shrinkage,porous bulges, and other issues.

Of the above two reasons, the second reason is typically the focus,while the first reason is less commonly considered. However, theexperimental results show that the harm of the first cause is fargreater than that of the second cause. Even using precise laser meltingcannot eliminate the adverse effects caused by the first cause. Theindustry often misjudges the defects caused by the first cause asimproper settings of melting equipment and parameters such astemperature curves. Engineers have made significant improvements inequipment and operating parameters. However, the uneven and unstablemelting of tin plating that has plagued the industry has not beensolved.

SUMMARY

A workpiece plating treatment method includes the steps of cleaning anouter surface of an outer plating layer of a workpiece to remove aplurality of oxides and dirt on the outer surface of the outer platinglayer, and reflow melting the outer plating layer of the workpiece usinga reflow melting device after the cleaning.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the present invention will become more apparent bydescribing in detail exemplary embodiments thereof with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic side view of a workpiece according to anembodiment;

FIG. 2 is a schematic side view of water shrinking into water dropletson the outer surface of the outer plating layer of the workpiece beforethe outer surface of the outer plating layer is cleaned;

FIG. 3 is a schematic side view of evenly spreading water onto the outersurface of the outer plating layer of the workpiece to form a uniformwater film after cleaning the outer surface of the outer plating layer;

FIG. 4 is a schematic side view of forming a protective film on theouter surface of the outer plating layer of the workpiece;

FIG. 5 is a schematic side view of a workpiece according to anotherembodiment; and

FIG. 6 is a schematic side view of forming a protective film on theouter surface of the outer plating layer of the workpiece shown in FIG.5 .

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present disclosure will be describedhereinafter in detail with reference to the attached drawings, whereinlike reference numerals refer to like elements. The present disclosuremay, however, be embodied in many different forms and should not beconstrued as being limited to the embodiments set forth herein; rather,these embodiments are provided so that the present disclosure willconvey the concept of the disclosure to those skilled in the art.

In the following detailed description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

As shown in FIG. 1 , in the illustrated embodiment, a workpiece 100includes a substrate 10 and an outer plating layer 11 formed on thesurface of the substrate 10. A method for processing the outer platinglayer 11 of the workpiece 100 shown in FIG. 1 will be described below.In an exemplary embodiment of the present invention, the methodcomprises the following steps:

S100: cleaning an outer surface of the outer plating layer 11 of theworkpiece 100 to remove oxides and dirt on the outer surface of theouter plating layer 11; and

S200: after step S100, the outer plating layer 11 of the workpiece 100is reflow melted using a reflow melting device.

FIG. 2 is an illustrative view of water shrinking into water droplets 1on the outer surface of the outer plating layer 11 of the workpiece 100before the outer surface of the outer plating layer 11 is subjected tocleaning treatment. FIG. 3 is an illustrative view in which water isevenly spread onto the outer surface of the outer plating layer 11 ofthe workpiece 100 to form a uniform water film 2 after cleaningtreatment.

As shown in FIGS. 2 and 3 , in the illustrated embodiment, aftercleaning the outer surface of the outer plating layer 11 of theworkpiece 100, the moisture content of the outer surface of the outerplating layer 11 will be increased, so that water can be evenly spreadon the surface of the workpiece 100. Similarly, when performing reflowmelting treatment on the outer plating 11 of the workpiece 100 using areflow melting device, the molten outer plating material will alsouniformly flow and lay evenly on the surface of the workpiece 100,avoiding the problems of shrinkage, porosity, and bulging of the moltenouter plating material, improving the uniformity and stability of theouter plating layer 11 during reflow melting. In the step S100, oxidesand dirt on the outer surface of the outer plating layer 11 of theworkpiece 100 can be removed using, for example, plasma, laser, flux, orany combination of the three to increase the moisture content of theouter surface of the outer plating layer 11.

In various embodiments, the reflow melting device used in the step S200can include at least one of a resistance wire melting furnace, aninfrared radiation melting furnace, an inductance melting furnace, and alaser melting furnace.

As shown in FIG. 1 , in an exemplary embodiment of the presentinvention, the aforementioned workpiece plating treatment method furthercomprises a step of:

S300: After step S200, the outer surface of the outer plating layer 11of the workpiece 100 is polished to flatten the outer surface of theouter plating layer 11.

In an exemplary embodiment of the present invention, in the step S300,for example, the workpiece 100 can be immersed in an optical polishingliquid to perform a chemical polishing treatment on the outer surface ofthe outer plating layer 11 of the workpiece 100. In another embodiment,in the step S300, for example, the outer surface of the outer platinglayer 11 of the workpiece 100 can be physically polished using aphysical polishing device. The physical polishing device may include asandblasting polishing device, a cloth wheel polishing device, or aplasma polishing device. In the step S300, a physical chemical mixingpolishing device can be used to perform a physical chemical mixingpolishing treatment on the outer surface of the outer plating layer 11of the workpiece 100.

FIG. 4 is an illustrative view of forming a protective film 12 on theouter surface of the outer plating layer 11 of the workpiece shown inFIG. 1 . As shown in FIGS. 1 and 4 , in the illustrated embodiment, theaforementioned workpiece plating treatment method also includes a stepof:

S400: After step S300, a protective film 12 is formed on the outersurface of the outer plating layer 11 of the workpiece 100.

In the step S400, the protective film 12 may include at least one of apassivation protective film, a lubricating oil protective film, and anano organic protective film. In the step S400, the outer surface of theouter plating layer 11 of the workpiece 100 can be passivated to form apassivation protective film on the outer surface of the outer platinglayer 11. In the step S400, the outer surface of the outer plating layer11 of the workpiece 100 can be lubricated to form a protective film oflubricating oil on the outer surface of the outer plating layer 11. Inan embodiment, in the step S400, the outer surface of the outer platinglayer 11 of the workpiece 100 can be sputtered to form a layer of nanoorganic protective film on the outer surface of the outer plating layer11.

In an exemplary embodiment of the present invention, a workpiecemanufacturing method is also disclosed, comprising the following steps:

S10: providing a workpiece 100 with an outer plating layer 11; and

S20: using the aforementioned workpiece plating treatment method totreat the outer plating layer 11 of the workpiece 100.

The aforementioned step S10 includes:

S11: providing substrate 10; and

S13: forming an outer plating layer 11 on the substrate 10.

In various embodiments, the outer plating layer 11 can be formed on thesurface of the substrate 10 by an electroplating process or anelectroless plating process.

FIG. 5 is an illustrative view of a workpiece 100 according to anotherexemplary embodiment of the present invention. FIG. 6 is an illustrativeview of forming a protective film 12 on the outer surface of the outerplating layer 11 of the workpiece 100 shown in FIG. 5 .

In the embodiment of FIGS. 5 and 6 , the aforementioned step S10 furthercomprises a step of:

S12: Before step 13, at least one intermediate plating layer 13 isformed on the substrate 10.

In various embodiments, the substrate 10 of the workpiece 100 may be acopper substrate, a steel substrate, or other suitable conductivesubstrate. The aforementioned at least one intermediate layer 13 mayinclude a nickel-plating layer and/or other suitable plating layer.

In various embodiments, the outer plating layer 11 on the workpiece 100may be a tin plating layer, an indium plating layer, a bismuth platinglayer, a lead plating layer, or other suitable metal or alloy platinglayer.

It should be appreciated for those skilled in this art that the aboveembodiments are intended to be illustrative, and not restrictive. Forexample, many modifications may be made to the above embodiments bythose skilled in this art, and various features described in differentembodiments may be freely combined with each other without conflictingin configuration or principle.

Although several exemplary embodiments have been shown and described, itwould be appreciated by those skilled in the art that various changes ormodifications may be made in these embodiments without departing fromthe principles and spirit of the disclosure, the scope of which isdefined in the claims and their equivalents.

As used herein, an element recited in the singular and proceeded withthe word “a” or “an” should be understood as not excluding plural ofsaid elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Moreover, unlessexplicitly stated to the contrary, embodiments “comprising” or “having”an element or a plurality of elements having a particular property mayinclude additional such elements not having that property.

What is claimed is:
 1. A workpiece plating treatment method, comprisingthe steps of: cleaning an outer surface of an outer plating layer of aworkpiece to remove a plurality of oxides and dirt on the outer surfaceof the outer plating layer; and reflow melting the outer plating layerof the workpiece using a reflow melting device after the cleaning. 2.The workpiece plating treatment method according to claim 1, furthercomprising: polishing the outer surface of the outer plating layer ofthe workpiece after the reflow melting to flatten the outer surface ofthe outer plating layer.
 3. The workpiece plating treatment methodaccording to claim 2, further comprising: forming a protective film onthe outer surface of the outer plating layer of the workpiece after thepolishing.
 4. The workpiece plating treatment method according to claim1, wherein the cleaning step includes using plasma, laser, flux, or anycombination of the three to remove the oxides and dirt on the outersurface of the outer plating layer of the workpiece.
 5. The workpieceplating treatment method according to claim 1, wherein the cleaning stepincreases a moisture content of the outer surface of the outer platinglayer.
 6. The workpiece plating treatment method according to claim 2,wherein, in the polishing step, the workpiece is immersed in an opticalpolishing liquid to perform a chemical polishing treatment on the outersurface of the outer plating layer of the workpiece.
 7. The workpieceplating treatment method according to claim 2, wherein, in the polishingstep, the outer surface of the outer plating layer of the workpiece isphysically polished using a physical polishing device.
 8. The workpieceplating treatment method according to claim 7, wherein the physicalpolishing device includes a sandblasting polishing device, a cloth wheelpolishing device, or a plasma polishing device.
 9. The workpiece platingtreatment method according to claim 2, wherein, in the polishing step,the outer surface of the outer plating layer of the workpiece issubjected to a physicochemical mixed polishing treatment.
 10. Theworkpiece plating treatment method according to claim 3, wherein theprotective film includes at least one of a passivation protective film,a lubricating oil protective film, and a nano organic protective film.11. The workpiece plating treatment method according to claim 3, whereinin forming step, the outer surface of the outer plating layer of theworkpiece is passivated to form a passivation protective film on theouter surface of the outer plating layer.
 12. The workpiece platingtreatment method according to claim 3, wherein, in the forming step, theouter surface of the outer plating layer of the workpiece is lubricatedto form a layer of lubricating oil protective film on the outer surfaceof the outer plating layer.
 13. The workpiece plating treatment methodaccording to claim 3, wherein, in the forming step, the outer surface ofthe outer plating layer of the workpiece is sputtered to form a layer ofnano organic protective film on the outer surface of the outer platinglayer.
 14. The workpiece plating treatment method according to claim 1,wherein the reflow melting device includes at least one of a resistancewire melting furnace, an infrared radiation melting furnace, aninductance melting furnace, and a laser melting furnace.
 15. A workpiecemanufacturing method, comprising steps of: providing a workpiece havingan outer plating layer; and processing the outer plating layer of theworkpiece using the workpiece plating treatment method according toclaim
 1. 16. The workpiece manufacturing method according to claim 15,wherein providing the workpiece includes providing a substrate andforming the outer plating layer on the substrate.
 17. The workpiecemanufacturing method according to claim 16, wherein providing theworkpiece includes forming an intermediate plating layer on thesubstrate before forming the outer plating layer on the substrate. 18.The workpiece manufacturing method according to claim 17, wherein thesubstrate is a copper substrate or a steel substrate.
 19. The workpiecemanufacturing method according to claim 18, wherein the intermediateplating layer includes a nickel plating layer.
 20. The workpiecemanufacturing method according to claim 15, wherein the outer platinglayer is a tin plating layer, an indium plating layer, a bismuth platinglayer, or a lead plating layer.